I've got the 1.2 update installed and have set up my gmail account, including the every-30-minutes check for new messages. But would doing this at public wifi hotspots have the risk of account info being stolen by Firesheep?

gmail lets you access mail securely - just be sure to set it up that way. See gmail help for instructions. You can also access it securely via the Nook browser at https://mail.google.com/. That way everything is encrypted between the device and gmail servers.